The present invention relates to the use of monoclonal antibodies to catalyze chemical reactions. Monoclonal antibodies are immunoglobulins produced by hybridoma cells. A monoclonal antibody reacts with a single antigenic determinant and provides greater specificity than a conventional, serum-derived antibody. Furthermore, screening a large number of monoclonal antibodies makes it possible to select an individual antibody with desired specificity, avidity and isotype. Hybridoma cell lines provide a constant, inexpensive source of chemically identical antibodies and preparations of such antibodies can be easily standardized. Methods for producing monoclonal antibodies are well known to those of ordinary skill in the art, e.g., Koprowski, H. et al., U.S. Pat. No. 4,196,265, issued Apr. 1, 1980.
Antigen recognition by a monoclonal antibody is attributable to a specific combining site in the N-terminal region of the immunoglobulin (Ig) molecule. Ig molecules are thought to react with antigens via the same types of short range forces characteristic of 11 protein-protein interactions. Antigen-antibody interactions are highly specific because of the complementary three-dimensional shapes of the antibody's combining site and of the corresponding antigenic determinant or epitope. Such complementary shapes permit the molecules to approach each other closely and to interact over a substantial surface area. The specificity of antibody-antigen interactions is evidenced by the fact that changes in the configuration of the antigenic determinant result in marked decreases in the binding constant of the antigen to the antibody. The binding constant of an antibody for its antigen is generally much higher than that of an enzyme for its substrate.
Uses of monoclonal antibodies are known. One such use is in diagnostic methods, e.g., David, G. and Greene, H., U.S. Pat. No. 4,376,110, issued Mar. 8, 1983.
Monoclonal antibodies have also been used to recover materials by immunoadsorption chromatography, e.g., Milstein, C., 1980, Scientific American 243:66, 70.
However, it has not been suggested that monoclonal antibodies can be used to catalyze chemical reactions. Indeed, the field of catalysis has developed independently from the field of immunology. The only reported attempt at using antibodies as catalysts of which applicants are aware resulted only in insignificant rate enhancement of the desired reaction. G.P. Royer, 1980, Advances in Catalysis 29:197-227.
During the course of a chemical reaction, the reactants undergo a series of transitions passing through different states until the products are reached. In molecular terms these transitions through intermediate states reflect changes in bond lengths, angles, etc. The transition from reactants to products may be viewed as involving formation of an intermediate which decomposes to produce the products. The overall rate of the reaction can be expressed in terms of the equilibrium constant characterizing the equilibria between the reactants, the intermediate and the products.
Catalysis can be regarded as a stabilization of the intermediate with respect to the state of the reactants. A catalyst is a substance that increases the rate of the reaction and is recovered substantially unchanged chemically at the end of the reaction. Although the catalyst is not consumed, it is generally agreed that the catalyst participates in the reaction.
Despite the commercial importance of catalysis, major limitations are associated with both simple chemical catalysis and enzymatic catalysis. Chemically catalyzed processes often do not produce high yields of desired products. Such processes often result in the production of impurities from side reactions. Furthermore, chemical catalysts are not known for many important chemical reactions. Other limitations include the relatively high cost of catalysts; the requirement for chemical activation; lack of utility under atmospheric conditions or in the presence of small amounts of water; and flammability or explosivity in the presence of atmospheric oxygen. Enzymatic catalysis depends on the existence and discovery of naturally occurring enzymes with the appropriate specificity and catalytic function needed to perform a particular reaction. Enzymes are unknown for many chemical reactions.
The present invention overcomes these limitations by providing a novel approach to catalysis. The invention provides a method for the preparation and use of monoclonal antibodies as convenient, readily obtainable and inexpensive catalysts having a degree of specificity and efficiency of action not previously achievable in the catalytic arts.